JavaScript 动态修改页面背景色与背景图片的实现

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<SCRIPT LANGUAGE=javascript>
function update(temp)
{
  if(temp == 'color')
  {
   document.body.style.backgroundColor="#FFFFFF";//改变背景色
  }
  if(temp == 'img')
  {
   document.body.style.backgroundImage="url(images/bgimg.gif)";//改变背景图片
  }
}
</SCRIPT>
</HEAD>
<BODY bgcolor="#CCFFFF">
<input type = button value="改变背景色" onclick="update('color')">
<input type = button value="改变背景图片" onclick="update('img')">
</BODY>
</HTML>